import React from "react";
import styled from "styled-components";

export default function App() {
    const StyledComponents = styled(Child)`
        background-color: blue;
        width: 100px;
        height: 100px;
    `

    return <div>
        <StyledComponents></StyledComponents>
    </div>;
}

function Child(props) {
    return <div className={props.className}>child</div>;
}